Re: ANALYZE sampling is too good

On 10/12/13 12:14, Heikki Linnakangas wrote:
>
>
> I took a stab at using posix_fadvise() in ANALYZE. It turned out to be 
> very easy, patch attached. Your mileage may vary, but I'm seeing a 
> nice gain from this on my laptop. Taking a 30000 page sample of a 
> table with 717717 pages (ie. slightly larger than RAM), ANALYZE takes 
> about 6 seconds without the patch, and less than a second with the 
> patch, with effective_io_concurrency=10. If anyone with a good test 
> data set loaded would like to test this and post some numbers, that 
> would be great.
>
>



I did a test run:

pgbench scale 2000 (pgbench_accounts approx 25GB).
postgres 9.4

i7 3.5Ghz Cpu
16GB Ram
500 GB Velociraptor 10K

(cold os and pg cache both runs)
Without patch:  ANALYZE pgbench_accounts    90s
With patch: ANALYZE pgbench_accounts  91s

So I'm essentially seeing no difference :-(

Regards

Mark